Adaptive directivity transmission device and method

ABSTRACT

A diversity receiver estimates a reception weight sing signals received at a plurality of antennas, a target pattern former forms a target radiation pattern based on the estimated reception weight, a transmission pattern former forms a transmission radiation pattern with a transmission weight using an arbitrary transmission weight as an initial value, a controller limits an angle range in which formation of the target radiation pattern and formation of the transmission radiation pattern are executed, an error detector detects an error between the target radiation pattern and the transmission radiation pattern, and subjects the detected error to logarithmic transformation, an updator updates the transmission weight so as to reduce the error subjected to logarithmic transformation, and a directivity former provides a transmission signal with a directivity according to the transmission radiation pattern formed using an updated transmission weight.

TECHNICAL FIELD

The present invention relates to an adaptive-directivity transmissionapparatus and adaptive-directivity transmission method that are appliedto, for example, a base station apparatus in a mobile communicationsystem.

BACKGROUND ART

An example of conventional adaptive-directivity transmission techniquesis explained. The adaptive-directivity transmission is a technique thatis studied on the premise that mainly a base station apparatus transmitsa signal to a mobile station such as a portable telephone in a mobilecommunication system. Specifically, the base station first estimates adirection of a place where the mobile station is present based onreception weight information obtained in a reception circuit such as anadaptive array antenna provided in the base station. Then, the basestation generates a directivity toward the estimated direction, andtransmits a signal to the mobile station. Since the base station thusperforms the adaptive-directivity transmission, it is possible toimprove a reception gain in the mobile station, andfurthertoreduceinterference to other mobile stations.

When this technique is used, in the case of a Time Division Duplex(hereinafter referred to as TDD) system in which transmission andreception carrier frequencies used in communications are same, it ispossible to use a reception weight as a transmission weight withoutmodifying the reception weight.

However, in the case of a Frequency Division Duplex (hereinafterreferred to as FDD) system in which transmission and reception carrierfrequencies used in communications are different, antenna intervalsdefined by a wavelength are different between a reception carrierfrequency and a transmission carrier frequency. Therefore, it is notpossible to obtain a directivity to be needed using the reception weightas the transmission with no modification performed. Accordingly, it isnecessary to perform a correction on the reception weight due to adifference between the reception and transmission frequencies.

As methods for correcting the difference between the reception andtransmission frequencies, there are following methods:

{circle around (1)} Convert reception weights into transmission weightscollectively using a predetermined conversion equation in the case wherean arrival direction of a received signal is recognized in advance, orwhere an arrival direction of a received signal is estimated;

{circle around (2)} obtain a transmission weight for forming atransmission radiation pattern (hereinafter referred to as “transmissionpattern”) with a directivity pointing only to an arrival direction of adesired signal, using a reception radiation pattern(hereinafter referredto as “reception pattern”) ; and

{circle around (3)} obtain a transmission weight for minimizing an errorbetween a reception pattern and a transmission pattern using apredetermined calculation equation with a negative feedback control.Thus, in the adaptive-directivity transmission in a conventional FDDsystem, the transmission weight is obtained from the reception weightwith the predetermined equation, and then the appropriate transmissionpattern is achieved.

However, in the above-described method {circle around (3)} ofcollectively converting, in the case where the transmission patternobtained with the transmission weights that are collectively convertedis compared to the reception pattern, the patterns of a portion around asignal arrival direction are approximate in both radiation patterns, buta difference between the transmission pattern and the reception patternbecomes large in the portion away from the signal arrival direction asthe portion goes away therefrom.

Further, in the above-described method {circle around (3)} of obtaininga transmission weight for minimizing an error between a receptionpattern and a transmission pattern using a predetermined calculationequation, the approximation is poor in a direction where an antennadirective gain is extremely suppressed, called null point. Furthermore,since it is necessary to examine a pattern error for all directions (0°to 360°) on the two-dimensional plane, this method requires a lot oftime and calculation amounts by the time a value of the obtainedtransmission weight converges.

The null point is generated to suppress the interference signal, forexample, when a base station receives the interference signal against adesired signal at the time the desired signal is received from mobilestation A. Therefore, since it is considered that another base station Bis present at the direction of the null point, in the case where thebase station performs the adaptive-directivity transmission to mobilestation A, if the base station suppresses a signal transmission level tothe direction of the null point, the interference in mobile station B isthereby reduced. Accordingly, it is important, for the improvement ofthe system performance, to obtain the transmission pattern of which thenull point is approximated to that in the reception pattern.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide an adaptive-directivitytransmission apparatus and adaptive-directivity transmission methodwhich can improve the approximation of a transmission pattern andreception pattern at a directive antenna gain suppressed direction,while being capable of reducing a time and calculation amount requiredby the time a value of transmission weight converges, in the case ofusing the method for obtaining a transmission weight that minimizes anerror between the transmission pattern and reception pattern with apredetermined calculation equation.

To achieve the above object, the adaptive-directivity transmissionapparatus according to the present invention subjects the error betweenthe transmission pattern and reception pattern to logarithmictransformation, and obtains a transmission weight that minimizes theerror subjected to the logarithmic transformation. The directive antennagain is generally represented using dB as a unit. The directive antennagain at a null point is normally smaller than the maximum value of thedirective antenna gain by 30 dB to 40 dB. Otherwise, the gain at thenull point is {fraction (1/1,000)} to {fraction (1/10,000)} the maximumvalue in the true value. Accordingly, since the error between thetransmission pattern and reception pattern around the null point becomesan extremely small value,in the adaptive-directivity transmissionapparatus according to the present invention the error is calculatedusing dB, not the true value. In the adaptive-directivity transmissionapparatus according to the present invention it is thus possible toimprove the approximation of the transmission pattern and receptionpattern at the directive antenna gain suppressed direction.

Further, to achieve the above object, the adaptive-directivitytransmission apparatus of the present invention limits a range in whichthe error between the transmission pattern and reception pattern issearched to a predetermined range. In the adaptive-directivitytransmission apparatus according to the present invention it is therebypossible to reduce the time and calculation amount required by the timethe value of transmission weight converges.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of anadaptive-directivity transmission apparatus according to a firstembodiment of the present invention;

FIG. 2 is a block diagram illustrating a configuration of a weightcorrection circuit in the adaptive-directivity transmission apparatusaccording to the above first embodiment;

FIG. 3A, FIG. 3B and FIG. 3C are radiation pattern diagrams for use inthe above first embodiment;

FIG. 4 is a block diagram illustrating a configuration of anadaptive-directivity transmission apparatus according to a secondembodiment of the present invention;

FIG. 5 is a block diagram illustrating a configuration of a weightcorrection circuit in the adaptive-directivity transmission apparatusaccording to the above second embodiment;

FIG. 6 is a diagram illustrating an arrangement of antennas of a basestation, and settings of radio signal arrival angles and radio signaltransmission angles to respective antennas, in the adaptive-directivitytransmission apparatus of the above second embodiment;

FIG. 7 is a radiation pattern diagram for use in the above secondembodiment;

FIG. 8 is a block diagram illustrating a configuration of anadaptive-directivity transmission apparatus according to a thirdembodiment of the present invention;

FIG. 9 is a block diagram illustrating a configuration of a weightcorrection circuit in the adaptive-directivity transmission apparatusaccording to the above third embodiment;

FIG. 10 is a diagram illustrating object ranges and directivities ofsector antennas in the third embodiment of the present invention;

FIG. 11 is a radiation pattern diagram for use in the above thirdembodiment;

FIG. 12 is a block diagram illustrating a configuration of anadaptive-directivity transmission apparatus according to a fourthembodiment of the present invention;

FIG. 13 is a block diagram illustrating a configuration of a weightcorrection circuit in the adaptive-directivity transmission apparatusaccording to the above fourth embodiment;

FIG. 14 is a radiation pattern diagram for use in the above fourthembodiment;

FIG. 15 is a flow chart to explain weight correction processing in theadaptive-directivity transmission apparatus according to the abovefourth embodiment;

FIG. 16 is a block diagram illustrating a configuration of anadaptive-directivity transmission apparatus according to a fifthembodiment of the present invention;

FIG. 17 is a block diagram illustrating a configuration of a weightcorrection circuit in the adaptive-directivity transmission apparatusaccording to the above fifth embodiment;

FIG. 18 is a radiation pattern diagram for use in the above fifthembodiment; and

FIG. 19 is a flowchart to explain weight correction processing in theadaptive-directivity transmission apparatus according to the above fifthembodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of an adaptive-directivity transmission apparatus andadaptive-directivity transmission method of the present invention areexplained below specifically using drawings.

First Embodiment

FIG. 1 is a block diagram illustrating a configuration of anadaptive-directivity transmission apparatus according to the firstembodiment of the present invention.

In FIG. 1, 100 is a mobile station with two antennas 101 and 102 (forexample, car telephone), and 103 is a base station which performs radiocommunications with mobile station 100. Base station 103 has thefunction as a delay apparatus for other network systems, further has aplurality (in this example, 4) of antennas 104 to 107, and using theantenna group, transmits and receives radio signals to/from antennas 101and 102 of mobile station 100.

Four analog signals received at antennas 104 to 107 of base station 103are converted into intermediate-frequency signals and amplified inreception RF section 108, and then inputted to radio signal processingsection 109, respectively.

Four analog signals inputted to radio signal processing section 109 aresubjected to quadrature demodulation in demodulation circuit 110. Thedemodulated signals are converted into digital signals in A/D converter111, and then inputted to baseband signal processing section 112.

Four digital signals that are inputted to baseband signal processing 112are weighted in diversity reception circuit 113 to be combined, and thendecoded in data detector 114. The decoded signal is transmitted toanother network system via interface section 115.

On the other hand, a signal inputted to baseband signal processingsection 112 via interface section 115 from another network system ismodulated in modulator 116, and then inputted to beam forming circuit118.

In beam forming circuit 118, the modulated signals are provided with thedirectivity using transmission weights which are obtained in weightcorrection circuit 117 using values of reception weights obtained indiversity reception circuit 113, and thus four transmission signals aregenerated. Four transmission signals are converted into signals with theradio carrier frequency in transmission RF section 119, and thentransmitted respectively from antennas 104 to 107 to mobile station 100.

FIG. 2 is a block diagram illustrating a configuration of weightcorrection circuit 117. As illustrated in FIG. 2, weight correctioncircuit 117 is comprised of target radiation pattern(hereinafterreferred to as “target pattern”) forming circuit 201 which forms atarget pattern based on reception weight Wr obtained in diversityreception circuit 113, transmission pattern forming circuit 202 whichforms a transmission pattern using transmission weight Wt, errordetection section 205 comprised of error detection circuit 203 whichdetects an error between the target pattern and a transmission patternand logarithmic transformation circuit 204 which subjects the detectederror to logarithmic transformation, and update section 206 whichupdates transmission weight Wt so as to reduce the error.

FIG. 3 is a radiation pattern diagram for use in the first embodiment.In FIG. 3, FIG. 3(a), FIG. 3(b) and FIG. 3(c) respectively illustratereception pattern 300, target pattern 301 and transmission pattern 302subjected to transmission weight correction according to the firstembodiment, and target pattern 301 and transmission pattern 303subjected to transmission weight correction according to theconventional method.

Operations in weight correction circuit 117 are explained below usingFIG. 1 to FIG. 3.

When reception weight Wr is estimated in diversity reception circuit 113using arrival radio signals from mobile station 100, target patternforming circuit 201 forms reception pattern 300 with reception weightWr. Further, target pattern forming circuit 201 converts receptionpattern 300 into target pattern 301 according to an arbitrary algorithm.Then, target pattern 301 is outputted to error detection section 205. Inaddition, in the first embodiment, as an example of the algorithms forconverting reception pattern 300 into target pattern 301, used is theconversion method of converting all directions except main lobes intodirective antenna gain suppressed directions.

On the other hand, transmission pattern forming circuit 202 formstransmission pattern 302 using reception weight Wr as an initial value,and outputs transmission pattern 302 to error detection section 205.

In error detection section 205, error detection circuit 203 firstdetects an error between target pattern 301 and transmission pattern302. Then, logarithmic transformation circuit 204 subjects the erroramount to logarithmic transformation, and outputs the logarithmic erroramount to update section 206.

Update section 206 updates transmission weight Wt so as to reduce theerror based on the logarithmic error amount according to a predeterminedalgorithm.

As described above, weight correction circuit 117 executes a series ofprocessing of formation of transmission pattern, error detection andupdate of transmission weight Wt the predetermined number of times, oruntil the error converges on a constant value, thereby formingtransmission pattern 302.

Thus, according to the first embodiment, since weight correction circuit117 subjects the error amount to logarithmic transformation, it ispossible to use an error at a direction where the directive antenna gainis small also effectively in updating transmission weight Wt. As aresult, it is possible to improve the approximation at the directiveantenna gain suppressed direction.

In addition, in the first embodiment, although reception weight Wr isused as the initial value of transmission weight Wt, it may be possibleto use any other value. Further, it may be possible to use receptionpattern 300 as the target pattern.

Second Embodiment

FIG. 4 is a block diagram illustrating a configuration of anadaptive-directivity transmission apparatus according to the secondembodiment of the present invention. In addition, in the secondembodiment illustrated in FIG. 4, each section with the sameconfiguration as that in the first embodiment illustrated in FIG. 1 isgiven the same symbol to omit explanations thereof.

The different point of the second embodiment illustrated in FIG. 4 fromthe first embodiment illustrated in FIG. 1 is a configuration of aweight correction circuit indicated with symbol 401 in FIG. 4. FIG. 5 isa block diagram illustrating a configuration of weight correctioncircuit 401.

Weight correction circuit 401 illustrated in FIG. 5 is comprised oftarget pattern forming circuit 501 which forms a target pattern based onreception weight Wr obtained in diversity reception circuit 113,transmission pattern forming circuit 502 which forms a transmissionpattern using transmission weight Wt, error detection section 503 whichdetects an error between the target pattern and the transmissionpattern, update section 504 which updates transmission weight Wt so asto reduce the error, and correction control circuit 505 which performsthe control of an error detection range and update range of transmissionweight Wt.

FIG. 6 is a diagram illustrating an arrangement of antennas of a basestation, and settings of radio signal arrival angles and radio signaltransmission angles to respective antennas, in the adaptive-directivitytransmission apparatus of the second embodiment.

FIG. 7 is a radiation pattern diagram for use in the second embodiment.In FIG. 7, 700 is a target pattern, 701 is a transmission patternsubjected to transmission weight correction according to the secondembodiment, and 702 is a transmission pattern subjected to transmissionweight correction according to the conventional method with alldirections used as the object range. In addition, it is assumed in thisembodiment to use the reception pattern as target pattern 700.

Characteristic operations of the second embodiment are explained belowusing FIG. 5 to FIG. 7.

In the second embodiment, based on a signal vector with same levels inall the direction (steering vector) that can be obtained from incidentangle θ of a received signal being incident upon each of antennas 104 to107 of which the arrangement is preset, an angle range is obtained inwhich a radiation pattern forms mirror images, and the range for theupdate or other processing on transmission weight Wt performed incorrection control circuit 505 is limited to a predetermined anglerange, thereby making it possible to reduce the calculation amount.

The specific explanation is described below. Steering vector X(θ)obtained from the antenna arrangement illustrated in FIG. 6 is expressedwith the following equation (1).

X(θ)=[exp{jπ(sin θ)}, exp{j2π(sin θ)}, exp {j3π(sin θ)}, exp{j4π(sinθ)}]  (1)

It is understood that X(θ) forms mirror images along: the 90° line as acenter from the definition of trigonometric function sine θ.Accordingly, since reception weight Wr adopts a single value and thereception pattern forms mirror images in ranges of −90°≦θ≦90° and90°≦θ≦270°, the range of −90°≦θ≦90° is preset in correction controlcircuit 505 as an angle range in which the error detection and update oftransmission weight Wt are executed.

In weight correction circuit 401, target pattern forming circuit 501controlled by correction control circuit 505 forms target pattern 700 inthe range of −90°≦θ≦90° with reception weight Wr.

On the other hand, transmission pattern forming circuit 502 formstransmission pattern 701 using reception weight Wr as an initial value.Then, error detection section 503 detects an error between targetpattern 700 and transmission pattern 701. Based on the detected error,update section 504 updates transmission weight Wt so as to reduce theerror according to the predetermined algorithm. At this point,correction control circuit 505 controls the angle range, in which theformation of transmission pattern 701, the error detection, and theupdate of transmission weight Wt are executed, at −90°≦θ≦90°.

As described above, weight correction circuit 401 executes a series ofprocessing of the formation of transmission pattern 701, errordetection, and update of transmission weight Wt in the predeterminedangle range (−90°≦θ≦90°) the predetermined number of times, or until theerror converges on a constant.

Thus, according to the second embodiment, since the range in which theseries of processing such as the update of transmission weight Wt isexecuted is limited to the predetermined angle range (−90°≦θ≦90°), it ispossible to reduce the calculation amount required for the series ofprocessing, while holding the correction accuracy with almost the samedegree, as compared to the case where the series of processing isexecuted with all directions (all-angle range) used as the object range.

In addition, in the second embodiment, although the reception pattern isused as the target pattern, it may be possible to form a target patternusing reception weight Wr with the other algorithm. Further, althoughreception weight Wr is used as an initial value of transmission weightWt, it may be possible to use the other arbitrary values.

Third Embodiment

FIG. 8 is a block diagram illustrating a configuration of anadaptive-directivity transmission apparatus according to the thirdembodiment of the present invention. In addition, in the thirdembodiment illustrated in FIG. 8, each section with the sameconfiguration as that in the second embodiment illustrated in FIG. 4 isgiven the same symbol to omit explanations thereof.

The different points of the third embodiment illustrated in FIG. 8 fromthe second embodiment illustrated in FIG. 4 are that antennas 104 to 107are sector antennas, and that weight correction circuit 801 limits anangle range for the weight correction processing corresponding to thedirectivities of sector antennas 104 to 107.

FIG. 9 is a block diagram illustrating a configuration of weightcorrection circuit 801. In addition, FIG. 10 is a diagram illustratingobject ranges and directivities of sector antennas 104 to 107.

Further, FIG. 11 is a radiation pattern diagram for use in the thirdembodiment. In FIG. 11, 1100 is a target pattern, 1101 is a transmissionpattern subjected to transmission weight correction according to thethird embodiment, and 1102 is a transmission pattern subjected totransmission weight correction according to the conventional method withall directions used as the object range. In addition, it is assumed inthis embodiment to use the reception pattern as target pattern 1100.

As described above, since the third embodiment has the feature that theangle range for the weight correction processing is limitedcorresponding to the directivities of sector antennas 104 to 107, it isassumed that as the angle range in which the error detection and updateof weight are executed, −70°≦θ≦70° is preset in correction controlcircuit 905 illustrated in FIG. 9 based on the antenna directivityillustrated in FIG. 10.

In weight correction circuit 801, target pattern forming circuit 901controlled by correction control circuit 905 forms target pattern 1100in the range of −70°≦θ70° with reception weight Wr.

On the other hand, transmission pattern forming circuit 902 formstransmission pattern 1101 using reception weight Wr as an initial value.Then, error detection section 903 detects an error between targetpattern 1100 and transmission pattern 1101. Based on the detected error,update section 904 updates transmission weight Wt so as to reduce theerror according to the predetermined algorithm. At this point,correction control circuit 905 controls the angle range, in which theformation of transmission pattern 1101, error detection, and update oftransmission weight Wt are executed, at −70°≦θ≦70°.

As described above, weight correction circuit 801 executes a series ofprocessing of the formation of transmission pattern 1101, errordetection, and update of transmission weight Wt in the predeterminedangle range (−70°θ≦70°) the predetermined number of times, or until theerror converges on a constant.

Thus, according to the third embodiment, it is possible to furtherreduce the calculation amount without the correction accuracydeteriorates as compared to the second embodiment.

In addition, in the third embodiment, although the reception pattern isused as the target pattern, it may be possible to form a target patternusing reception weight Wr with the other algorithm. Further, althoughreception weight Wr is used as an initial value of transmission weightWt, it may be possible to use other arbitrary values.

Fourth Embodiment

FIG. 12 is a block diagram illustrating a configuration of anadaptive-directivity transmission apparatus according to the fourthembodiment of the present invention. In addition, in the fourthembodiment illustrated in FIG. 12, each section with the sameconfiguration as that in the third embodiment illustrated in FIG. 8 isgiven the same symbol to omit explanations thereof.

The different point of the fourth embodiment illustrated in FIG. 12 fromthe third embodiment illustrated in FIG. 8 is that in the case where anangle range for the weight correction processing is limited to anarbitrary range by weight correction circuit 1201, the series ofprocessing of the formation of transmission pattern, error detection andupdate of transmission weight is executed to the end point of thelimited angle range, and repeated again to another end point of thelimited angle range. Thus, the processing is executed in the limitedangle range forth and back alternately, i.e., in the mutually reversedirections.

FIG. 13 is a block diagram illustrating a configuration of weightcorrection circuit 1201. As illustrated in FIG. 13, weight correctioncircuit 1201 is comprised of target pattern forming circuit 1301 whichforms a target pattern based on reception weight Wr obtained indiversity reception circuit 113, transmission pattern forming circuit1302 which forms a transmission pattern using transmission weight Wt,error detection section 1303 which detects an error between the targetpattern and the transmission pattern, update section 1304 which updatestransmission weight Wt so as to reduce the error, and correction controlcircuit 1305 which performs the control of an error detection range, andupdate range and update direction of transmission weight Wt.

FIG. 14 is a radiation pattern diagram for use in the fourth embodiment.In FIG. 14, 1400 is a target pattern, 1401 is a transmission patternsubjected to transmission weight correction according to the fourthembodiment, and 1402 is a transmission pattern, subjected to thetransmission weight correction, formed in the third embodiment (updateonly in one direction). In addition, it is assumed in this embodiment touse the reception pattern as target pattern 1400.

Characteristic operations of the fourth embodiment are explained belowwith reference to a flowchart illustrated in FIG. 15. In addition, it isassumed in the fourth embodiment that the angle range for the update isset at −70°≦θ≦70°.

In weight correction circuit 1201, first, target pattern forming circuit1301 controlled by correction control circuit 1305 forms target pattern1400 in the range of −70°≦θ≦70° with reception weight Wr.

Next, in weight correction circuit 1201, the series of processing of theformation of transmission pattern 1401, error detection, and update oftransmission weight Wt is executed according to the flowchartillustrated in FIG. 15.

Specifically, first, at step (hereinafter referred as “ST”) 1501,correction control circuit 1305 substitutes −70° for θ, and transmissionpattern forming circuit 1302 forms transmission pattern 1401 at −70°.

Next, at ST1502, error detection sect ion 1303 detects an error at −70°between target pattern 1400 and transmission pattern 1401, and based onthe detected error, update section 1304 updates transmission weight Wtso as to reduce the error according to the predetermined algorithm.

Next, at ST1503, correction control circuit 1305 increases θ by anarbitrary angle interval (=Δθ).

Then, at ST1504, correction control circuit 1305 decides whether θreaches the end of the angle range for the processing (70°), and when θdoes not reach the end point, the processing flow returns to ST1502, andthe processing of ST1502 to ST1504 is repeated. On the other hand, whenθ reaches the end point, at ST1505, correction control circuit 1305substitutes +70° for θ and transmission pattern forming circuit 1302forms transmission pattern 1401 at +70°.

In other words, in weight correction circuit 1201, the series ofprocessing of the formation of transmission pattern 1401, errordetection, update of transmission weight Wt is sequentially executedrepeatedly until θ reaches +70° starting from −70°, thus formingtransmission pattern 1401 in the range of −70° to +70°.

Next, ST1506, error detection section 1303 detects an error at +70°between target pattern 1400 and transmission pattern 1401, and based onthe detected error, update section 1304 updates transmission weight Wtso as to reduce the error according to the predetermined algorithm.

Next, at ST1507, correction control circuit 1305 decreases θ by anarbitrary angle interval (=Δθ).

Then, at ST1508, correction control circuit 1305 decides whether θreaches the other end of the angle range for the processing (−70°), andwhen θ does not reach the other end point, the processing flow returnsto ST1506, and the processing of ST1506 to ST1508 is repeated. On theother hand, when θ reaches the other end point, at ST1509, correctioncontrol circuit 1305 decides whether or not the error converges on aconstant value. When the error does not converges on the constant value,the processing flow returns to ST1501 to repeat the processing of ST1501to ST1509, and when the error converges on the constant value, theprocessing is finished.

Thus, according to the fourth embodiment, in the case where the anglerange for the processing is limited to a half range or an arbitraryrange, it is possible to reduce the deterioration of accuracy ofradiation pattern approximation due to effects of discontinuity at theend points of the angle range for the processing.

In addition, in the fourth embodiment, although the angle range for theprocessing is set at −70°≦θ≦70°, and the starting point is set at −70°,it may be possible to employ any angle range and any starting point.Further, although the reception pattern is used as the target pattern,it may be possible to form a target pattern using reception weight Wrwith the other algorithm. Furthermore, although reception weight Wr isused as an initial value of transmission weight Wt, it may be possibleto use the other arbitrary values.

Fifth Embodiment

FIG. 16 is a block diagram illustrating a configuration of anadaptive-directivity transmission apparatus according to the fifthembodiment of the present invention. In addition, in the fifthembodiment illustrated in FIG. 16, each section with the sameconfiguration as that in the fourth embodiment illustrated in FIG. 12 isgiven the same symbol to omit explanations thereof.

The different point of the fifth embodiment illustrated in FIG. 16 fromthe fourth embodiment illustrated in FIG. 12 is that when weightcorrection circuit 1601 executes the series of processing of theformation of transmission pattern, error detection and update oftransmission weight the predetermined number of times, or until theerror converges on a constant value repeatedly at arbitrary angleintervals Δθ , weight correction circuit 1601 executes the processingshifting the angle at which the processing is executed, while holdingangle interval Δθ, and interpolates further finely in angle interval Δθ,thus making it possible to reduce the calculation amount with thecorrection accuracy kept.

FIG. 17 is a block diagram illustrating a configuration of weightcorrection circuit 1601. As illustrated in FIG. 17, weight correctioncircuit 1601 is comprised of target pattern forming circuit 1701 whichforms a target pattern based on reception weight Wr obtained indiversity reception circuit 113, transmission pattern forming circuit1702 which forms a transmission pattern using transmission weight Wt,error detection section 1703 which detects an error between the targetpattern and the transmission pattern, update section 1704 which updatestransmission weight Wt so as to reduce the error, and correction controlcircuit 1705 which performs the control of an error detection range, andupdate range and update direction of transmission weight Wt.

FIG. 18 is a radiation pattern diagram for use in the fifth embodiment.In FIG. 18, 1800 is a target pattern, 1801 is a transmission patternsubjected to transmission weight correction according to the fifthembodiment, and 1802 is a transmission pattern subjected to transmissionweight correction at a fixed angle for the processing. In addition, itis assumed in this embodiment to use the reception pattern as targetpattern 1800.

Characteristic operations of the fifth embodiment are explained belowwith reference to a flowchart illustrated in FIG. 19. In addition, it isassumed in the fifth embodiment that the angle range for the update isset at 0°≦θ≦360°.

In weight correction circuit 1601, first, target pattern forming circuit1701 controlled by correction control circuit 1705 forms target pattern1800 in the range of 0°≦θ<360° with reception weight Wr.

Next, in weight correction circuit 1601, the series of processing of theformation of transmission pattern 1801, error detection, and update oftransmission weight Wt is executed according to the flowchartillustrated in FIG. 19.

Specifically, first, at ST1901, correction control circuit 1705substitutes 0° for α that is a starting point of the above-mentionedseries of processing.

Next, at ST1902, correction control circuit 1705 substitutes (0°+α) forθ , and transmission pattern forming circuit 1302 forms transmissionpattern 1801 at 0°.

Next, at ST1903, error detection section 1703 detects an error at 0°between target pattern 1800 and transmission pattern 1801, and based onthe detected error, update section 1704 updates transmission weight Wtso as to reduce the error according to the predetermined algorithm.

Next, at ST1904, correction control circuit 1705 increases θ byarbitrary angle interval Δθ(Δθ=10° in the fifth embodiment).

Then, at ST1905, correction control circuit 1705 decides whether θexceeds 360° (360°<θ), and when θ does not exceed 360°, the processingflow returns to ST1903, and the processing of ST1903 to ST1905 isrepeated. On the other hand, when 360°<θ, at ST1906, correction controlcircuit 1705 increases starting point α by Δα (Δα=2° in the fifthembodiment).

Next, at ST1907, correction control circuit 1705 decides whetherstarting point a reaches 10° (10°≦α), and when starting point α does notreach 10°, the processing flow returns to ST1902, and the processing ofST1902 to ST1907 is repeated. On the other hand, when 10°≦α, at ST1908,correction control circuit 1705 decides whether or not the errorconverges on a constant value. When the error does not converges on theconstant value, the processing flow returns to ST1901, and theprocessing of ST1901 to ST1908 is repeated. When the error converges onthe constant value, the processing is finished.

Thus, weight correction circuit 1601 executes the series of processingof the formation of transmission pattern 1801, error detection andupdate of transmission weight Wt to the other end shifting startingpoint α from 0° to 8° by Δα (Δα=2° in the fifth embodiment).

Thus, according to the fifth embodiment, it is possible to reduce thecalculation amount with the converge rate increased, thereby making itpossible to improve the accuracy for following changes of environments.

In addition, in the fifth embodiment, although the reception pattern isused as the target pattern, it may be possible to form a target patternusing reception weight Wr with the other algorithm. Further, althoughreception weight Wr is used as an initial value of transmission weightWt, it may be possible to use the other arbitrary values.

As described above, according to the present invention, it is possibleto handle a range of error variation due to the variation of directiveantenna gain such as 10^(−n) time (n is an integer number) with highaccuracy, thereby making it possible to improve the approximation of thedirective antenna gain suppressed direction.

Further, it is possible to simplify the processing section for forming atarget pattern, thereby making it possible to reduce the entireprocessing amount.

Furthermore, in the case where an arbitrary axis around which theradiation pattern forms mirror images is present in any direction within360° in the directivity on a horizontal plane for an antenna, the errordetection and update of transmission weight are executed in half therange of mirror images, and modified for 360° when the radiation patternis formed. As a result, it is possible to reduce the calculation amountwith the correction accuracy held at almost the same degree, as comparedto the case where the error detection and update of transmission weightare executed in all directions.

Moreover, by using the directivities of sector antennas, and limitingthe processing to be executed to the radiation pattern in a range closeto that for reception to be executed, it is possible to further reducethe calculation amount as compared to the case where the processing isexecuted in a half of all directions (range of 180°).

Further, in the case where the angle range for the processing is limitedto a half range or an arbitrary range, it is possible to reduce thedeterioration of accuracy of radiation pattern approximation due toeffects of discontinuity at the end points of the angle range for theprocessing.

Furthermore, it is possible to reduce the calculation amount with theconverge rate increased, thereby making it possible to improve theaccuracy for following changes of environments.

This application is based on the Japanese Patent Application No.HEI10-177525 filed on Jun. 24, 1998, entire content of which isexpressly incorporated by reference herein.

Industrial Applicability

The present invention is applicable to, for example, a base stationapparatus and mobile station apparatus in mobile communication systems.

What is claimed is:
 1. An adaptive-directivity transmission apparatuscomprising: a diversity receiver which estimates a reception weightusing signals received at a plurality of antennas; a target patternformer which forms a target radiation pattern based on an estimatedreception weight; a transmission pattern former which forms atransmission radiation pattern with a transmission weight using anarbitrary transmission weight as an initial value; a controller whichlimits an angle range in which formation of said target radiationpattern and formation of said transmission radiation pattern areexecuted; an error detector which detects an error between said targetradiation pattern and said transmission radiation pattern; an updatorwhich updates said transmission weight so as to reduce a detected error;and a directivity former which provides a transmission signal with adirectivity according to said transmission radiation pattern formedusing an updated transmission weight.
 2. The adaptive-directivitytransmission apparatus according to claim 1, wherein said error detectorsubjects the detected error to logarithmic transformation, and saidupdator updates the transmission weight so as to reduce said errorsubjected to the logarithmic transformation.
 3. The adaptive-directivitytransmission apparatus according to claim 1, wherein said target patternformer forms a reception radiation pattern with an estimated receptionweight, and converts the reception radiation pattern into the targetradiation pattern according to an arbitrary algorithm, thereby formingsaid target radiation pattern based on said estimated reception weight.4. The adaptive-directivity transmission apparatus according to claim 1,wherein based on signal vectors for all directions obtained from signalincidence angles for a plurality of antenna configurations, saidcontroller detects an angle range in which the target radiation patternand transmission radiation pattern each forms mirror images, and limitsthe angle range in which the formation of said target radiation patternand the formation of said transmission radiation pattern are executed.5. The adaptive-directivity transmission apparatus according to claim 1,wherein in the case where the plurality of antennas are sector antennas,said controller sets an angle range corresponding to directivities of aplurality of sector antennas, and limits the angle range in which theformation of said target radiation pattern and the formation of saidtransmission radiation pattern are executed.
 6. The adaptive-directivitytransmission apparatus according to claim 1, wherein said controllerlimits an angle range in which the formation of said target radiationpattern and the formation of said transmission radiation pattern areexecuted, and increases an angle by a predetermined angle interval froma minimum angle to a maximum angle in a limited angle range, whiledecreasing the angle by said predetermined angle interval from saidmaximum angle to said minimum angle in said limited angle range.
 7. Theadaptive-directivity transmission apparatus according to claim 1,wherein said controller limits an angle range in which the formation ofsaid target radiation pattern and the formation of said transmissionradiation pattern are executed, and in a limited angle range, shifts astarting angle from which limitation is started to other arbitrarypoints sequentially, and increases an angle by a predetermined angleinterval from said starting angle from which the limitation is startedto a maximum angle for the limitation.
 8. A base station apparatusprovided with an adaptive-directivity transmission apparatus, saidadaptive-directivity transmission apparatus comprising: a diversityreceiver which estimates a reception weight using signals received at aplurality of antennas; a target pattern former which forms a targetradiation pattern based on an estimated reception weight; a transmissionpattern former which forms a transmission radiation pattern with atransmission weight using an arbitrary transmission weight as an initialvalue; a controller which limits an angle range in which formation ofsaid target radiation pattern and formation of said transmissionradiation pattern are executed; an error detector which detects an errorbetween said target radiation pattern and said transmission radiationpattern; an updator which updates said transmission weight so as toreduce a detected error; and a directivity former which provides atransmission signal with a directivity according to said transmissionradiation pattern formed using an updated transmission weight.
 9. Amobile station apparatus provided with an adaptive-directivitytransmission apparatus, said adaptive-directivity transmission apparatuscomprising: a diversity receiver which estimates a reception weightusing signals received at a plurality of antennas; a target patternformer which forms a target radiation pattern based on an estimatedreception weight; a transmission pattern former which forms atransmission radiation pattern with a transmission weight using anarbitrary transmission weight as an initial value; a controller whichlimits an angle range in which formation of said target radiationpattern and formation of said transmission radiation pattern areexecuted; an error detector which detects an error between said targetradiation pattern and said transmission radiation pattern; an updatorwhich updates said transmission weight so as to reduce a detected error;and a directivity former which provides a transmission signal with adirectivity according to said transmission radiation pattern formedusing an updated transmission weight.
 10. A mobile communication systemhaving a base station apparatus provided with an adaptive-directivitytransmission apparatus and a mobile station apparatus provided with theadaptive-directivity transmission apparatus, said adaptive-directivitytransmission apparatus comprising: a diversity receiver which estimatesa reception weight using signals received at a plurality of antennas; atarget pattern former which forms a target radiation pattern based on anestimated reception weight; a transmission pattern former which forms atransmission radiation pattern with a transmission weight using anarbitrary transmission weight as an initial value; a controller whichlimits an angle range in which formation of said target radiationpattern and formation of said transmission radiation pattern areexecuted; an error detector which detects an error between said targetradiation pattern and said transmission radiation pattern; an updatorwhich updates said transmission weight so as to reduce a detected error;and a directivity former which provides a transmission signal with adirectivity according to said transmission radiation pattern formedusing an updated transmission weight.
 11. An adaptive-directivitytransmission method comprising: the diversity receiving step ofestimating a reception weight using signals received at a plurality ofantennas; the target pattern forming step of forming a target radiationpattern based on an estimated reception weight; the transmission patternforming step of forming a transmission radiation pattern with atransmission weight using an arbitrary transmission weight as an initialvalue; the control step of limiting an angle range in which formation ofsaid target radiation pattern and formation of said transmissionradiation pattern are executed; the error detection step of detecting anerror between said target radiation pattern and said transmissionradiation pattern; the update step of updating said transmission weightso as to reduce a detected error; and the beam forming step of providinga transmission signal with a directivity according to said transmissionradiation pattern formed using an updated transmission weight.
 12. Theadaptive-directivity transmission method according to claim 11, whereinin said error detection step, the detected error is subjected tologarithmic transformation, and in said update step, the transmissionweight is updated so that said error subjected to the logarithmictransformation is reduced.
 13. The adaptive-directivity transmissionmethod according to claim 11, wherein in said target pattern formingstep, a reception radiation pattern is formed using an estimatedreception weight, and the reception radiation pattern is converted intothe target radiation pattern according to an arbitrary algorithm,whereby said target radiation pattern is formed based on said estimatedreception weight.